Early oral protein-containing diets following elective lower gastrointestinal tract surgery in adults: a meta-analysis of randomized clinical trials

BACKGROUND: Although current guidelines make consensus recommendations for the early resumption of oral intake after surgery, a recent comprehensive meta-analysis failed to identify any patient-centered benefits. We hypothesized this finding was attributable to pooling studies providing effective protein-containing diets with ineffective non-protein liquid diets. Therefore, the aim of this paper was to investigate the safety and efficacy of early oral protein-containing diets versus later (traditional) feeding after elective lower gastrointestinal tract surgery in adults. METHODS: PubMed, Embase, and the China National Knowledge Infrastructure databases were searched from inception until 1 August 2019. Reference lists of retrieved studies were hand searched to identify randomized clinical trials reporting mortality. No language restrictions were applied. Study selection, risk of bias appraisal and data abstraction were undertaken independently by two authors. Disagreements were settled by obtaining an opinion of a third author. Majority decisions prevailed. After assessment of underlying assumptions, a fixed-effects method was used for analysis. The primary outcome was mortality. Secondary outcomes included surgical site infections, postoperative nausea and vomiting, serious postoperative complications and other key measures of safety and efficacy. RESULTS: Eight randomized clinical trials recruiting 657 patients were included. Compared with later (traditional) feeding, commencing an early oral protein-containing diet resulted in a statistically significant reduction in mortality (odds ratio [OR] 0.31, P = 0.02, I(2) = 0%). An early oral protein-containing diet also significantly reduced surgical site infections (OR 0.39, P = 0.002, I(2) = 32%), postoperative nausea and vomiting (OR 0.62, P = 0.04, I(2) = 37%), serious postoperative complications (OR 0.60, P = 0.01, I(2) = 25%), and significantly improved other major outcomes. No harms attributable to an early oral protein-containing diet were identified. CONCLUSIONS: The results of this systematic review can be used to upgrade current guideline statements to a grade A recommendation supporting an oral protein-containing diet commenced before the end of postoperative day 1 after elective lower gastrointestinal surgery in adults. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13741-021-00179-3.